In a vehicle equipped with a power transmission mechanism having an automatic transmission having an input shaft coupled to a drive source mounted on the vehicle and an output shaft connected to the input shaft via a hydraulic clutch, juddering of the clutch of the automatic transmission may occur due to the difference between input and output rotational speeds, rendering the vehicle occupant to have uncomfortable feeling. The juddering becomes remarkable as the deterioration of the clutch progresses.
It has hitherto been proposed by Patent Reference 1 to suppress juddering in a power transmission mechanism equipped with a torque converter, if the juddering of a lockup clutch is detected when a slip amount of the lockup clutch is controlled to a desired value, by correcting the desired slip amount to increase.